Reamers are devices intended to remove tissue and bone from the human body. Specifically, the reamer of the present invention is designed to remove tissue from the cotyloid cavity of the acetabulum in preparation for the insertion of a hip joint supported by a prosthetic cup seated in the cavity.
In general, acetabular reamers are constructed with a continuous partially hemispherical surface. This partial hemispherical structure is ideally suited to create a cavity in which to fit a prosthetic cup. Prosthetic cups generally have a curved exterior surface that is inserted into the cotyloid cavity.
A series of discrete tissue cutting openings are typically positioned throughout the outer partially hemispherical surface and extend through the reamer wall thickness. These tissue cutting openings are characteristically designed such that the specific surface that cuts the tissue is provided within the perimeter of the opening.
Many problems are associated with these traditional reamer designs such as prior art reamer designs found in U.S. Pat. Nos. 7,217,272, 6,001,105, and 5,299,893 to Salyer as well as U.S. Pat. No. 6,951,563 to Wolford. One is that prior art reamers tend to generate heat as they cut bone and tissue during an orthopedic surgical procedure. In some cases, these reamers are connected to motors that rotate the attached reamer at speeds in excess of 1,000 RPM. In addition, a significant amount of torque is generated against the reamer as it is applied to bone and tissue. As a result, heat is generated at the cutting site as the reamer is used. This heat may cause necrosis of bone and tissue that is adjacent to the reamer. Furthermore, such heat generation may cause the cutting surface of the reamer to become damaged.
Prior art reamers are typically composed of stainless steel, which is not an efficient conductor of heat. Stainless steel has a relatively low coefficient of thermal conductivity of about 16 W·m−1·K−1. As a result, heat that is generated during use of a stainless steel reamer, typically becomes concentrated at the tissue cutting edge. The present invention, therefore, provides a reamer cutting device that is at least partially constructed with a material having increased thermal conductivity properties, more preferably, a material with an increased coefficient of thermal conductivity that removes heat from the tissue cutting surface.
The reamer of the present invention is thus designed to divert heat away from the cutting surface, thus minimizing heat generation during use thereby, reducing the possibility of causing tissue necrosis, patient trauma, and potential reamer structural damage. Heat that is generated during use of the reamer is removed from the cutting surface that is in physical contact with bone and tissue.